PRESIDENT Rodrigo R. Duterte’s former police chief on Tuesday said he would block any attempts — if he becomes president next year — by the International Criminal Court (ICC) to probe alleged human rights violations committed in the country’s war on drugs.

“I will not only protect President Duterte but also myself because we are co-accused in the case,” Senator Ronald M. Dela Rosa, who is running for President next year, told the ABS-CBN News Channel.

The lawmaker, who enforced the state’s anti-illegal drug campaign as Mr. Duterte’s police chief, said he would allow ICC investigators to visit the Philippines to “observe” but not to investigate.

An investigation by the Hague-based tribunal would be a slap in the face for Philippine courts that are still functioning, he added.

The ICC has ordered an investigation of Mr. Duterte’s crackdown on illegal drugs that has killed thousands, as it found “reasonable basis” that crimes against humanity might have been committed.

“The ICC works under the presumption of noncooperation of the accused,” human rights lawyer and senatorial aspirant Neri Colmenares said in a statement. “Whether or not Dela Rosa and Duterte cooperate, the ICC will find a way to investigate, prosecute and punish them.”

The presidential palace has said the Philippines would not cooperate with the ICC probe because it lost jurisdiction of the case after the country broke ties with the tribunal in 2019. The withdrawal would not affect the probe, according to the ICC.

Mr. Dela Rosa denied claims that the Duterte administration had committed crimes against humanity and criticized the report of Amnesty International on drug war-related deaths.

Tens of thousands of drug suspects whom police claimed had resisted arrest died in raids, according to the United Nations. The Philippine Commission on Human Rights has accused the state of violating human rights by abetting police abuses.

Meanwhile, Mr. Dela Rosa said ex-Senator Ferdinand “Bongbong” R. Marcos, Jr. should not apologize for human rights violations committed under his father’s two-decade rule.

“The sins of the father should not be blamed on his child.”

The late dictator Ferdinand E. Marcos stole as much as $10 billion (P503 billion) from the Filipino people, according to government estimates, earning him a Guinness World Record for the “greatest robbery of a government.“

He was ousted by a street uprising in 1986 that forced him and his family to go into exile in the United States.

The Philippine government has recovered P174 billion of the assets, according to the Presidential Commission on Good Government.

More than 70,000 people were jailed, about 34,000 were tortured and more than 3,000 people died under the dictator’s martial rule, according to Amnesty International.

Mr. Dela Rosa, whom the ruling PDP-Laban picked as its presidential bet two hours before the deadline, earlier said he would give up his slot to Davao City Mayor and presidential daughter Sara Duterte-Carpio if she runs for president.

Under the law, Ms. Carpio may be substituted for Mr. de la Rosa as long as she becomes a member of the party. The substitution period is allowed until mid-November.

Fitch Solutions Country Risk and Industry Research earlier said Mr. Dela Rosa would probably focus on crime and mirror Mr. Duterte’s leadership style if he becomes president.

Mr. Dela Rosa vowed to push changes to economic provisions of the 1987 Constitution and relax foreign ownership rules.

Antonio A. Ligon, a law and business professor at De La Salle University, said foreign investors are attracted to countries that respect human rights and promote democratic values.

Investors are closely watching the views of Philippine presidential candidates on human rights, he said in a text message.

“What good is there in making profit when human beings who are supposed to enjoy the fruit of investments are being treated unfairly and unjustly by violating their human rights?” Mr. Ligon asked. “A good number of investors give due consideration to this.” — Kyle Aristophere T. Atienza